The hormone angiotensin II has several prominent actions concerning body fluid balance which are mediated by the central nervous system. Among these effects are water intake, secretion of antidiuretic hormone, and a pressor effect. One identified site of action of angiotensin II is the subfornical organ. Recent data have also indicated that the tissue bordering the optic recess of the third ventricle, and including the organum vasculosum laminae terminalis, may also possess receptors for the hormone. The interrelationships between these receptor loci, in terms of the central effects of angiotensin, will be studied. The involvement of these structures in hypertension will be explored, and concentrations of angiotensin required to provoke drinking with intravenous vs. intracranial applications will be studied. The synergy between central effects of angiotensin, in the context of the behaving, unanesthetized animal, will be emphasized in these studies.